This invention relates to a writing instrument with a movable closure and, more particularly, to a writing instrument with a movable closure which is fabricated to repeat the operations of projecting a writing nib of a writing unit from an opening in a barrel to a writing position, and retracting and storing the writing unit in an airtight environment within the barrel in a closed or non-writing position.
Various proposals have been made to provide snap means such as a closure, for the writing instrument nib of the aforementioned type of writing instrument. Structures have been suggested, by way of example, which are adapted to project the writing nib into the writing position by using an actuating member which is caused to press down on an elastic rubber cover or the like with a cut or slit or to press on and thereby open a snap cover mounted on the barrel end. The first mentioned structure offers the advantage of simple construction. Notwithstanding, the pen element directly rubs the elastic rubber cover to occasionally imperil a snap function if it is frequently, repeatedly operated. Direct adhesion of ink to the pen element over long use deteriorates the rubber to impede the sealing effect. Also, the pen point is subjected to damage due to the repeated use thereof.
On the other hand, the second pressure mechanism with the actuating member, undoubtedly overcomes defects inherent in the prior art. However, the construction in which the snap cover is exposed to a holder end, is deficient in that damage to the exposed portion may result. Further, this construction fails to exhibit satisfactory performance as to durability, and airtightness after many repeated operations. This limits the design of the writing instrument nib. Therefore, the known structure which incorporates the snap cover in the holder end is lacking in reliability, durability, and airtightness.